Mail handling apparatus



May 16, 1961 l. MATHIS MAIL HANDLING APPARATUS 2 Sheets-Sheet 1 Filed March 28, 1958 Q u m@ w a N U- l 1 NW MN N NM )3 x l m mwi NW.\ N, W w\ m Q\ N N N H N wwvaw WWTLNM May 16, 1961' l. MATHIS 2,984,349

MAIL HANDLING APPARATUS Filed March 28, 1958 2 Sheets-Sheet 2 I I II I 75 g h I I l r 1 4 1% "I j I 87 I m4 62 '"fl Tamra/a I 44 /05 I og I I f I2 81 y; 70 MOTOR I 74 I l e i IN VENT OR flew/v6 MA TH/S fl 7. 4. BY

ATTORNEY-5' United States Patent MAIL HANDLING APPARATUS Irving Mathis, Silver Spring, Md., assignor to Emerson Radio & Phonograph Corporation, Jersey City, N..!., a corporation of New York Filed Mar. 28, 1958, Ser. No. 724,646

8 Claims. (Cl. 20974) The present invention relates to apparatus and systems for handling and sorting fiat light articles and especially letters. In our current economy the expeditious handling and processing of mail has become vital to the eflicient conduct of business and communications. The volume of mail pieces has become so large as to encumber and literally swamp postal facilities, especially at the metropolitan post oilices handling many million pieces of mail daily. The problems of conveying, cancelling and sorting this great volume of varied shapes and sizes of mail pieces have heretofore not been efficiently solved resulting not only in delays of deli-very of mail, but also uneconomic utilization of supplies, equipment and manpower.

The present invention is particularly adapted for use with (but not limited to) mail handling apparatus described and claimed in the copending application Serial No. 683,284 of Milton A. Stovall for Mail Handling Apparatus, filed September 11, 1957, now Patent No. 2,961,085; the copending application Serial No. 696,393 of C. G. Makrides for Mail Handling Apparatus, filed November 14, 1957, now Patent No. 2,905,309; and copending application Serial No. 686,529 of R. F. Blake, S. I. Goodman and J. J. Rudigier for Automatic Mail Cancelling Apparatus, filed September 26, 1957, now abandoned, all of which are assigned to the same assignee as the present application.

The apparatus of these prior applications is suitable for accepting bulk letter mail such as may be obtained from any mail bag and to convert such bulk mail into a rapid stream of single mail pieces traveling at a high speed of the order of 150 inches per second. The individual pieces of this stream of mail are oriented in a vertical plane with their longer edges horizontal but are otherwise unfaced and may have the stamps carried on the front face or reverse face, at the top or at the bottom, or at the leading edge or trailing edge, of the envelope. This single-file stream of letter pieces enters a cancelling apparatus which automatically applies a cancellation imprint at the exact position of the stamp on the envelope despite the fact that the stamp may occur at different positions on different letters and despite any unevenness of separation or repetition of letters in the stream.

The present invention utilizes such a stream of mail and is particularly concerned with providing apparatus that sorts the stream of letters into several groups in response to electrical signals which may, for example correspond to predetermined characteristics of such mail.

A further object of the present invention is to provide an apparatus that will gate or direct into several channels predetermined articles from a stream of individual articles flowing at a high rate of speed and yet cause no interruption in the flow of the stream.

Another object of the present invention is to provide means for automatically gating or directing letters into groups in accordance with electrical signals, which may, for example correspond to theposition of the stamp on the envelope, or the absence of any stamp.

Patented May 16, 1961 These and other objects of the present invention will become more fully apparent from a consideration of the following description of a preferred embodiment, taken in conjunction with the appended drawings, in which:

Fig. l is a diagram showing a part of a general mail handling system incorporating the present invention;

Fig. 2 is a plan view of a form of gating apparatus according to the present disclosure;

Fig. 3 is a side elevation view of the gating apparatus of Fig. 2 viewed along lines 33;

Fig. 4 is a cross-sectional view of the apparatus of Fig. 3 taken along lines 44; and

Fig. 5 is a diagram showing the various usual orientations of stamped envelopes.

The input to the present invention is supplied in the form of a high, substantially constant-speed flow of single mail pieces standing vertically on their long edges, with a predetermined minimum spacing between the pieces. This stream of mail is illustratively derived from the output of an automatic sensing and cancelling apparatus indicated generally at 10 in Fig. l, which may be of the form shown in the above-mentioned Blake et al. application.

In the input stream of mail to the sensing and cancelling apparatus 10 there are, in general, four major orientations which an envelope may assume in relation to the location of the stamp, as shown in Fig. 5. At A is shown the normal orientation of the envelope 22 with the stamp 23 in the upper right hand corner. In this orientation the front of the envelope with the address 24 and the stamp 23 is facing frontwards (as viewed in the drawing) with the address 24 in normal reading position. At B the envelope 22 is shown with its reverse side facing frontwards and the envelope 22 itself is upside down with the stamp 23 now in the lower right hand corner facing the rear. At C the envelope 22 is shown with its address 24 and stamp 23 facing frontwards but upside down with respect to A so that the address 24 is now inverted and stamp 23 is in the lower left hand corner At D envelope 22 is in the upright position but having its reverse side facing the front so that the stamp 23 is now to the rear in the upper left hand corner.

If, in each instance, the envelope 22 is considered to be moving from right to left as shown by arrow 26, the stamp 23 in views A and B will be at the trailing edge of the envelope 22, while stamp 23 in views C and D will be at the leading edge of the envelope 22. Also, at A and D the stamps 23 will be at the upper edge of the envelope 22, while at B and C the stamps 23 will be at the lower edge. Accordingly, the envelopes may be segregated into five categories, according to the location of the stamps thereon, as follows:

(1) Envelopes with stamps in the upper trailing edge of the front face (view A);

(2) Envelopes with stamps in the lower trailing edge of the rear face (view B);

(3) Envelopes with stamps in the lower leading edge of the front face (view C);

(4) Envelopes with stamps in the upper leading edge of the rear face (view D); and

(5) Envelopes with no stamps at all or with stamps at other positions than as in 1 to 4.

In the maner described in detail in the above mentioned Blake et al. application the continuous stream of letter mail in single file enters the sensing and cancelling apparatus 10 travelling in a direction as indicated by arrow 30, and passes two sensing units 31 and 32; 32 cooperates with the front face of each letter and 3-1 with the rear face. Each of these sensing units produces electrical signals corresponding to the presence and position of the stamp appearing on each letter as it passes the sensing unit. These electrical signals are utilized to activate the cancelling units 33 and 34 in the cancelling apparatus to apply a cancellation mark to the envelope and postage stamp at a subsequent point in its travel without interrupting the flow of the letter pieces even though this flow may be at the high rate of 30,000 pieces per hour.

It will be seen from the Blake et al. application that the stream of letters passing through the cancelling apparatus has the stamps cancelled regardless of the position of the stamp on the envelope, that is regardless of whether the stamp is on the front face or rear face of the envelope and regardless of whether it is at the upper or lower edge of the envelope. In some instances, such as where there have been no stamps on the envelope or where they have been placed in such positions as not to be sensed by the sensing units 31 or 32 letters will pass through the cancelling apparatus without operation of the cancelling units 33 or 34 at all.

It is desirable to be able to sort out and keep together mail pieces from the cancelling apparatus having certain characteristics. Thus, envelopes having no stamps should be separated from those bearing stamps. Similarly, it may be desired to separate short envelopes (for example, less than 6 inches in length) from long envelopes (illustratively 6 to 12 inches long). For facing the cancelled envelopes preliminary to routing them to their addressed destinations, it may be desired to separate those having stamps on their front faces from those having stamps on their rear faces, and to separate those having stamps near their leading edges from those with stamps near the trailing edges.

The present invention permits accomplishment of these results by providing an apparatus responsive to suitable electrical signals for separating letters of a rapidly flowing stream into groups without any change in speed. By synchronizing these signals to the passage of the letters, the present invention utilizes these signals to divert the letters and sort them so that, for example all letters of relatively similar length can be grouped having their stamps in the same corresponding position.

Some of the grouping arrangements possible are illustrated and described in copending application Serial No. 732,330 of S. I. Goodman and J. I. Rudigier for Mail Handling Equipment filed May 1, 1958, and assigned to the same assignee as the present invention. That application also describes and claims the apparatus for producing electrical signals representative of the various characteristics of letters to be sorted out, and reference is made to it for a more complete disclosure of that part of the present system. In essence, each envelope produces a signal representative of predetermined characteristics of that envelope, and by the present invention that signal is used to direct its corresponding envelope to a proper channel or receptacle.

An illustrative system for successive sorting according to such characteristics include a series of gating or directing units in three stages as shown in Fig. 1. A single directing unit 46 is provided in Stage I which functions to accept a continuous inter-mixed stream of mail at its input 47 and to divert along a channel indicated at 48 all letters of all sizes in which the stamp occurs at or adjacent to the leading edge of the envelope, but regardless of whether the stamp is located on the front face or rear face of the envelope, corresponding to C and D of Fig. 5. All other envelopes including those which are to be rejected and those which have the stamp occurring adjacent the trailing edge of the envelope whether on the rear or front face, continue undiverted along path 49 to stage II where a further directing unit indicated at 51 performs a similar directing action by diverting along a path 52 all letters regardless of size having the stamp at the trailing edge whether on the front or rear face, corresponding to A and B of Fig. 5.

In this way, all envelopes that provide proper indication of stamp location are diverted either along the path 48 or along path 52, leaving all other envelopes for passage along path 49 into the reject category. These latter reject envelopes will include those on which no stamp appears, so that no indication of stamp location was derived, as well as envelopes on which improper stamp or equivalent matter appears. For example, as indicated in the description of the sensing units in the Blake et al. application above, if the stamp area on the letter has a length exceeding a predetermined maximum, such as of the order of three inches, the cancelling apparatus is arranged so that it will not cancel such a stamp and the directing units 46 and 51 are arranged to pass such envelopes undiverted to the reject pile.

In stage III two identical directing units 53 and 54 are provided which divert along respective paths 56 and 57 all envelopes supplied to the input which have a length exceeding a predetermined value, such as six inches. In this way all long envelopes are diverted along paths 56 and 57, while the envelopes under six inches, called short envelopes, are continued along paths 48 and 52.

Thus the envelopes are segregated into five groups, namely, long envelopes with stamps at the leading edge, whether front or back, short envelopes with stamps at the leading edge, whether front or back, rejects, short envelopes with stamps at the trailing edge whether front or back, and long envelopes with stamps at the trailing edge whether front or back.

The manner in which the directing operation is performed in directing units 46, 51, 53 and 54 is the same. To all intents and purposes these units are identical except with respect to the particular control signals applied thereto. By way of illustration of all of them, the directing unit 54 is described in detail.

A friction drive roller 61 is continuously rotated in the sense indicated by the arrow adjacent to it in Fig. 2 by means of a shaft 62 to which is coupled a pulley 63 rotated by a belt 64 driven by a suitable motor and pulley not shown. A similar roller 66 is driven by a shaft 67 coupled to pulley 68 which is rotated by belt 69 driven from another or the same motor means. These rollers 61 and 66 are of the same diameter and rotate continuously at the same angular velocity. A pair of idler rollers 71 and 72 are freely rotatably mounted in their respective brackets 73 and 74 and resiliently urged together. These brackets 73 and 74 are fixed respectively to posts 76 and 77 secured in a cross bar 78. Cross bar 78 is secured to a shaft 79 by means of a set screw 80 which shaft is coaxial with the tangential line of contact between rollers 71 and 72 and forms a pivot shaft about which the pair of rollers 71 and 72 will rotate. Shaft 79 is rotatably mounted in a pair of bearing blocks 108 and 109, with block 108 at the shafts remote end and block 109 intermediate of the shafts ends. Bearing blocks 108 and 109 are fixed depending from bars 111 by bolts 112 and 113 received in hollow posts 114 and 115 respectively. Clamped to shaft 79 at 81 is an arm 82 which is pivotally connected at 83 to an adjustable tie arm 90, with the remote end of arm pivotally connected to the armature arm of electromagnet or solenoid 87. Depending between the pair of electromagnets or solenoids 86 and 87, is a link 84. In this instance, in Fig. 4 electromagnet 87 is indicated as energized while electromagnet 86 is deenergized and accordingly link 84 and arm 90 have been displaced to the rightward or clockwise as seen in Fig. 4, thereby rotating shaft 79 and cross arm 78 affixed thereto clockwise, which urges roller 71 into contact with driven roller 66 as shown in Fig. 2. In this. way roller 71 is continuously driven from roller 66, and roller 72, which is maintained resiliently urged against roller 71, is also continuously rotated. Accordingly, as the letter enters the gating unit 54 along the path indicated at 52 in Fig. 2, either by driven transport means preceding this point of the system or by its own inertia after being ejected from the preceding stage, it is drawn between the rotating rollers 71 and 72 and ejected in this instance along a straight path through a further pair of rollers 89 and 91. .It will be noted that by proper choice of the angular speed of rollers 66 in conjunction with the radius of rollers 71 and 72 the peripheral speed of rollers 71 and 72 can be equal to the velocity of the letters or varied therewith.

Roller 89 is continuously driven by its shaft 92 to which is secured a pulley 93 engaging a belt 94 which is also engaged by a pulley 95 on shaft 67. Roller 91 is an idler roller pivotally mounted on an arm 96 which is pivoted at 97 and urged in a counterclockwise direction as seen in Fig. 2 by a tension spring 98 whereby roller 91 is maintained in frictional engagement with driven roller 89 and both rollers 89 and 91 serve to grasp and transport forward any letter passed to them by the rollers 71 and 72. The pivotal mounting of roller 91 permits the passage of letters of varying width up to the maximum of the system, illustratively one-quarter inch in one example, without interfering with the lineal speed of the letters passing therethrough.

When a signal is supplied to the electromagnet 86 (and at the same time the excitation of electromagnet 87 is terminated) link 84 and arm 90 will be displaced to the left or counterclockwise as seen in Fig. 4 thereby rotating shaft 79 and cross arm 78 in a counterclockwise direction also causing rollers 71 and 72 likewise to pivot in a counterclockwise sense so that roller 72 is in frictional engagement with the driven roller 61 and roller 71 is out of engagement with roller 66 so that in this position both rollers 72 and 71 are driven by roller 61. The electrical signal produced in response to the passage of an envelope is properly timed by the system of the Goodman et al. application to energize the proper electromagnet of the directing unit at substantially the instant that the envelope which created that signal has its leading edge arriving at or just passing between the rollers. Thus for directing unit 54 electromagnet 86 is excited when an envelope that is designated as a long by the sensing ;unit and control circuit has its leading edge arriving between rollers 71 and 72. These rollers will pivot with the envelope therebetween and will assume a position whereby the plane joining the axes of rollers 71 and 72 instead of being parallel to the plane joining the axes of rollers 39 and 91, as in Fig. 2, will instead be nearly parallel to the plane joining the axes of a further pair of rollers 101 and 102. Roller 102 is continuously driven by a shaft 103 to which is coupled a pulley 104 engaging a belt 105 which in turn engages a pulley 106 secured to the rotating shaft 62. In this way roller 102 is continuously driven in the sense indicated by the arrow adjacent it in Fig. 2. Roller 101 is an idler roller similar in construction and operation to roller 91 already described. In this way, upon energization of electromagnet 86 an envelope having a proper length to constitute a long is diverted from the straight path represented by rollers 89 and 91 to the diverted path represented by rollers 101 and 102 into the guide or chute 107. It will be understood that the gating rollers 71 and 72 will remain in the diverted position long enough for the letter passing therethrough to be grasped by the following rollers 101 and 102, after which the gate may restore itself to its normal position shown in the drawings.

This gating or directing may be accomplished without in any way reducing the linear speed of the letters passing therethrough, and over fairly wide angles of the order of 30 to 45 degrees. Subsequent pairs of rollers similar to 1m, M2 or $9, 91, may be used for the further transport of the letters to maintain them at their uniform speed. In this way high speed gating and sorting of the letters in response to electrical signals is accomplished, which signals may represent stamp location or size of letter or other characteristic, as may be desired.

It will be understood of course that signals represent ing characteristics other than stamp position and envelope length to be sorted or gated could also be used, and that this kind of gating apparatus is in no sense limited to use with letters but can similarly be used with' respect to other articles, particularly those which are fiat.

Since many apparently widely differing structures may be readily devised by those skilled in the art without departing from the scope of the present invention, it is understood that the foregoing is illustrative only, the scope of the present invention being defined solely by the appended claims.

What is claimed is:

1. An apparatus for directing letters of a constant velocity input stream of single vertical pieces in response to electrical signals representative of the presence and location of stamps upon said letters and the length of said letters, comprising: a pair of equal-diameter idler rollers having their axes parallel to the plane in which the said stream of letters flow, means resiliently urging said idler rollers together into frictional engagement with one another in the absence of a letter therebetween, means pivotally mounting said idler rollers as a unit with only two rest positions, a first position being with one idler roller on one side of the path of said letters and the other idler roller on the other side of said letter path with the line of contact of said rollers intersecting the path of said stream of letters and with the line joining the axes of said rollers perpendicular to said path, the other position being with the line joining said idler roller axes at an angle to the said letter path with said line of contact remaining in said letter path, a first driven roller on one side of the said letter path frictionally engaging one of said idler rollers when said idler rollers are in their first position, a second driven roller on the other side of said letter path frictionally engaging the other of said idler rollers when said idler rollers are in said second position, means for rotating said driven rollers at a peripheral speed equal to the linear speed of said letters whereby said idler rollers are given a like peripheral speed equal to said letter linear speed, solenoid means coupled to said idler roller unit and respon sive to said electrical signals for moving said idler rollers from said first position into said second position synchronously with the entry between said idler rollers of a letter corresponding to said signal, whereby those letters corresponding to such electrical signals are sorted out from the stream of letters, allowing the remainder of the said stream to continue undiverted, and means for con veying all said letters as said letters emerge from between said idler rollers, said means including a pair of rollers, means resiliently urging said rollers together with their line of contact along said letter path, and means for rotating said last mentioned rollers at a peripheral speed equal to the linear speed of said letters, and also including a further pair of rollers, means resiliently urging said further pair of rollers together with their line of contact along the path of said diverted letters, and means for rotating said further pair of rollers at a perpiheral speed equal to said letter linear speed.

2. An apparatus for directing letters of a constant velocity input stream in response to electrical signals representative of the presence and location of stamps upon said letters and the length of said letters, comprising: a pair of equal-diameter idler rollers having their axes parallel to the plane in which the said stream of letters flow, means resiliently urging said idler rollers together into frictional engagement with one another in the absence of a letter therebetween, means pivotally mounting said idler rollers as a unit with only two rest positions, a first position being with one idler roller on one side of the path of said letters and the other idler roller on the other side of said letter path with the line of contact of said rollers intersecting the path of said stream of letters and with the line joining the axes of said rollers being perpendicular to the said path, the other position being with the line joining said idler roller axes at an acute angle from the said letter path with said line of contact remaining in said letter path, a first driven roller on one side of the said letter path frictionally engaging one of said idler rollers when said idler rollers are in their first position, a second driven roller on the other side of said letter path frictionally engaging the other of said idler rollers when said idler rollers are in said second position, means for rotating said driven rollers at a peripheral speed equal to the linear speed of said letters whereby said idler rollers are given a like peripheral speed equal to said letter linear speed, solenoid means coupled to said idler roller unit and responsive to said electrical signals for moving said idler rollers from said first position into said second position synchronously with the entry between said idler rollers of a letter corresponding to said signal, whereby those letters corresponding to such electrical signals are sorted out from the stream of letters, allowing the remainder of the said stream to continue undiverted, and means for receiving all said letters as said letters emerge from between said idler rollers.

3. An apparatus for directing flat, light articles of a continuously moving input stream in response to signals representative of the presence of predetermined characteristics of said articles, comprising: a pair of idler rollers having their axes parallel to the plane in which the said stream of articles flow, means resiliently urging said idler rollers together into frictional engagement with one another in the absence of an article therebetween, means pivotally mounting said idler rollers as a unit with only two rest positions, a first position being with the idler roller unit astride the path of said articles with the line of contact of said rollers intersecting the path of said stream of articles and with the line joining the axes of said rollers being perpendicular to said path, the other position being with the line joining said idler roller axes at an angle to the said article path, means for rotating said idler rollers at a peripheral speed equal to the linear speed of said articles, means responsive to said signals for moving said idler rollers from said first position into said second position synchronously with the entry between said idler rollers of an article corresponding to said signal, whereby those articles corresponding to such signals are sorted out from the stream of articles, allowing the remainder of the said stream to continue undiverted, and means for receiving all said articles as said articles emerge from between said idler rollers.

4. An apparatus for directing letters of a constant velocity input stream of single vertical pieces inresponse to electrical signals representative of the presence and location of stamps upon said letters and the length of said letters, comprising: a pair of equal-diameter rollers having their axes parallel to the plane in which the said stream of letters flow, means resiliently urging said rollers together into frictional engagement with one another in the absence of a letter therebetween, means pivotally mounting said rollers as a unit with only two rest positions, it first position being with the rollers of said unit astride the path of said letters with the line of contact of said rollers intersecting the path of said stream of letters with the line joining the axes of said rollers being perpendicular to said path, the other position being with the line joining said idler roller axes at an angle to the said letter path with said line of contact remaining in said letter path, means for rotating said rollers at a peripheral speed equal to the linear speed of said letters, electromagnetic means coupled to said rollers and responsive to said electrical signals for moving said rollers from said first position into said second position synchronously with the entry between said rollers of a letter corresponding to said signal, whereby those letters corresponding to such electrical signals are sorted out from the stream of letters,

allowing the remainder of the said stream to continue undiverted, and means for conveying all said letters as said letters emerge from between said idler rollers.

5. Apparatus for directing letters of a constant velocity input stream in response to electrical signals representative of the presence and location of stamps upon said letters and the length of said letters, comprising: a pair of equal-diameter idler rollers having their axes parallel to the path of the said stream of letters, means resiliently urging said rollers together into frictional engagement with one another in the absence of a letter therebetween, means pivotally mounting said pair of idler rollers as a unit astride the path of said letters with the line of contact of said rollers intersecting the path of said stream of letters, means to rotate said idler rollers at a peripheral speed equal to the linear speed of said letters, electromagnetic means coupled to said idler rollers and responsive to said electrical signals for pivoting said idler rollers synchronously with the entry between said idler rollers of a letter corresponding to said electrical signal, whereby those letters corresponding to such electrical signals are sorted out from the stream of letters, allowing the remainder of said stream of letters to continue undivirted and means for conveying said letters as said letters emerge from between said idler rollers.

6. An apparatus for directing letters of a constant velocity input stream in response to electrical signals representative of the presence and location of stamps upon said letters and the length of said letters, comprising: a pair of equal-diameter rollers, means urging said rollers together, means pivotally mounting said rollers as a unit with said individual rollers astride the said letter path with the line of contact of said rollers intersecting the path of said stream of letters, means for rotating said rollers at a peripheral speed equal to the linear speed of said letters, electromagnetic means coupled to said idler rollers and responsive to said electrical signals for pivoting said rollers synchronously with the entry between said rollers of a letter corresponding to said signal, whereby those letters corresponding to such electrical signals are sorted out from the stream of letters, allowing the remainder of the said stream to continue undiverted, and means for conveying all said letters as said letters emerge from between said idler rollers.

7. Apparatus for directing letters according to stamp position and length of the envelope of said letters of a continuously moving stream of single vertical pieces comprising: means for transporting said letters at a constant velocity, a plurality of pairs of rollers with said pairs of rollers sequentially disposed along the path of said stream of letters, means for pivotally mounting each of said pairs of rollers, means normally urging the individual rollers of each of said pairs of rollers resilienty together to form a line contact, said line of contact positioned in said letter path, means for continuously rotating said rollers at a peripheral speed equal to the linear speed of said letters, electromagnetic means coupled to each of said pairs of rollers and each of said last mentioned means responsive to electrical signals representative of the occurrence and position of a postage stamp on and the length of one of said letters for selectively displacmg a corresponding pair of said rollers at an acute angle from the said letter path in time relation to the passage of said one letter, whereby those letters corresponding to such electrical signals are sorted out from said stream of letters allowing the remainder of said stream to continue undiverted, and means for conveying said letters as said letters emerge from between a said pair of rollers.

8. A mail directing unit for sorting letters from a continuously moving stream of letters in response to electrical signals corresponding to certain of said letters, comprising: a pair of rollers astride the said letter stream and between which the said letters pass, means resiliently urging said rollers together, means pivotally mounting said rollers about an axis in the path of said stream,

said last mentioned means being responsive to a predetermined one of said electrical signals for pivoting said rollers synchronously with the entry between said rollers of a letter corresponding to said electrical signal whereby those letters corresponding to such electrical signals are sorted out from the stream of letters allowing the remainder of said stream of letters to continue undiverted, and means for conveying said letters as said letters emerge from between said rollers.

References Cited in the file of this patent UNITED STATES PATENTS Hopp Feb. 20, 1917 Robinson Oct. 4, 1955 FOREIGN PATENTS Great Britain Jan. 20, 1954 

